Syrian regime forces advanced in Aleppo on Sunday after Russia unleashed dozens of air strikes in the battleground northern city overnight, a monitor and an AFP correspondent reported.

Among the targets of air raids during the night were the neighbourhoods of Bustan al-Basha, Sakhur and Suleiman al-Halabi, the correspondent reported.

"Dozens of Russian air strikes targeted overnight the fighting zones inside Aleppo city," said the Britain-based Syrian Observatory for Human Rights monitoring group.

Observatory director Rami Abdel Rahman said the raids "helped regime forces to advance in the north of the city" where they reached the outskirts of Al-Halaq district.

"Regime forces aims to control Bustan al-Basha and Sakhur districts to tighten the zones controlled by rebels," said Abdel Rahman.

Aleppo, once Syria's vibrant commercial powerhouse, is now at the heart of a major military campaign by President Bashar al-Assad's fighters and his steadfast ally Moscow.

The offensive, announced on September 22, has seen dozens of civilians killed and residential buildings flattened in the east, where an estimated 250,000 people live under government siege.

Diplomatic efforts to end the fighting across the country have all but collapsed.

However, the foreign ministers of the United States and Russia, which brokered a week-long truce deal that collapsed last month, spoke by phone on Saturday.

Russia said its Foreign Minister Sergei Lavrov spoke to his American counterpart John Kerry and they "examined the situation in Syria, including the possibility of normalising the situation around Aleppo".

It said "illegal armed groups" continue fighting in the city despite Russian-US agreements.

Since fighting first broke out in the city in 2012, Aleppo has been divided by a frontline between rebel forces in the east and government troops in the west.

Source : AFP